KCSE CHEMISTRY QUESTIONS AND ANSWERS PER TOPIC
a) Write an equation to show the effect of heat on the nitrate of:
(i) Potassium b) The table below gives information about elements A1,A2,A3, and A4
(i) In which period of the periodic table is element A2? Give a reason
(ii) Explain why the atomic radius of: I A1 is greater than that of A2; II A4 is smaller than its ionic radius (iii) Select the element which s in the same group as A3 (iv) Using dots (.) and crosses(x) to represent outermost electrons. Draw a diagram to show the bonding in the compound formed when A1 reacts with A4
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a) Biogas is a mixture of mainly carbon (IV) oxide and methane.
(i) Give a reason why biogas can be used as a fuel. (ii) Other than fractional distillation, describe a method that can be used to determine the percentage of methane in biogas. b) A sample of biogas contains 35.2% by mass of methane. A biogas cylinder contains 5.0 kg of the gas. Calculate the; (i) Number of moles of methane in the cylinder. (Molar mass of methane=16) (ii) Total volume of carbon (IV) oxide produced by the combustion of methane in the cylinder (Molar gas Volume=24.0 dm-3+ at room temperature and pressure). c) Carbon (Iv) oxide, methane, nitrogen (I) oxide and trichlorofluoromethane are green-house gases. (i) State one effect of an increased level of these gases to the environment. (ii) Give one source from which each of the following gases is released to the environment; I Nitrogen (i) oxide II Trichlorofluoromethane.
ANSWERS
(a) Neutralization
(b)(i)Calcium hydrogen carbonate (ii)Drying agent Extraction of sodium metal
Crude oil contains sulphur. What would be the effect to the environment of using fuel containing sulphur?
ANSWERS
A certain mass of a metal E1 reacted with excess dilute hydrochloric acid at 25°C. The volume of hydrogen gas liberated was measured after every 30 seconds. The results were presented as shown in the graph below.
a) Name one piece of apparatus that may have been used to measure the volume of gas liberated. b) (i) On the same axis, sketch the curve that would be obtained if the experiment was repeated at 35°C. (ii) Explain the shape of your curve in b(i) above.
ANSWERS
(a)(i)Cryolite
(ii)Electrolysis (b)Good conductor Does not rust Malleable Light High M.P Does not corrode easily
In an experiment to determine the percentage of magnesium hydroxide in an anti-acid, a solution containing 0.50 g of the anti-acid was neutralized by 23.0 cm3 of 0.010m hydrochloric acid (Relative formula mass of magnesium hydroxide =58)
a) Mass of magnesium hydroxide in the anti-acid; b) Percentage of magnesium hydroxide in the anti-acid
When solid B1 was heated, a gas which formed a white precipitate when passed through lime water was produced. The residue was dissolved in dilute nitric (V) acid to form a colourless solution B2. when dilute hydrochloric acid was added to solution B2 a white precipitate which dissolved on warning was formed.
a) Write the formula of the; I Cation in solid B1 II anion in solid B1 b) Write an ionic equation for the reaction between the resdue and dilute nitric (V) acid.
Distinguished between a strong and a weak acid. Give examples.
Diamond and graphite are allotropes of carbon. In terms of structure and bonding explain the following.
ANSWERS
(a)Cooling
(b)Latent heat of fusion
In a closed system, aqueous iron (III) chloride reacts with sulphide gas as shown in the equation below.
2FeCl3(aq) + H2S(g) → 2FeCl2(aq) 2HCl(aq) + S(s) State and explain the observation that would be made if dilute hydrochloric acid is added to the system at equilibrium.
a) State the Graham's law diffusion.
b) The molar masses of gases W and X are 16.0 and 44.0 respectively. If the rate of diffusion of W through a porous material is 12cm3s-1 calculate the rate of diffusion of X through the same material. ​Related Chemistry Questions and Answers on Gas Laws Form 3 Level
The grid below is part of the periodic table. Use it to answer the questions that follow, (the letters are not the actual symbols of the elements).
a) Indicate on the grid the position of an element represented by letter V whose atomic number is 14.
b) Select a letter which reaction between Q and T.
ANSWERS
(a)Amphoteric
(b)Lead (II), Zinc and Aluminium
Starting with copper metal, describe how a sample of crystals of copper (II) chloride may be prepared in the laboratory.
ANSWER
Samples of urine from three participants F, G and H at an international sports meeting were spotted onto a chromatography paper alongside two from illegal drugs A1 and A2.
A chromatogram was run using methanol. The figure below shows the chromatogram.
a) Identify the athlete who had used an illegal drug.
b) Which drug is more soluble in methanol?
ANSWERS
(a)A1
(b)A1 using baseline |
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